pH-responsive molecular assemblies of pyridylbutadiene derivative with cucurbit[7]urilElectronic supplementary information (ESI) available: Additional supporting graphs and method M1. See DOI: 10.1039/c8ra03355b

The interaction between red-emitting pyridinium derivative [4-((1 E ,3 E )-4-(4-(dimethylamino)phenyl)buta-1,3-dien-1-yl)-1-methylpyridin-1-ium] (DABP) and cucurbit[7]uril was investigated using optical absorption, steady-state and time-resolved fluorescence and anisotropy measurements. The changes in the UV/Vis absorption, fluorescence spectral characteristics and lifetime, with a change in pH, reveal efficient binding of CB7 to the dye molecule. The cucurbit[7]uril encapsulated DABP brings ∼1.5 units upward p K a shift. The formation of supramolecular assemblies with 1 : 1 and 2 : 1 host-guest stoichiometries with CB7 at different pH conditions have been verified from 1 H NMR, isothermal titration calorimetric studies and geometry optimization calculations. CB7-dye complexation and the ensuing morphological changes were revealed by SEM, AFM and optical microscopy images. This pH-responsive supramolecular assemblies of red-emitting DABP dye can find potential applications in biological imaging, optical pH-sensor and the construction of building blocks for the supramolecular architectures. pH-responsive emission behavior of supramolecular complexes between pyridylbutadiene with CB7 and formation of molecular assemblies is described.